Divided press



E. J. JUSTUS DIVIDED PRESS May 25, 1965 Filed Jan. 9, 1963 i INVENTOR.[dyar' d c/us ras TTORNE YS United States Patent 3,185,617 DIVHDED PRESSEdgar J. Justus, Beloit, Wis, assignor to Beloit Corporation, Beloit,Win, a corporation of Wiscensin Filed Jan. 9, 1963, Ser. No. 250,351 3Claims. (Cl. 162-274) This invention relates to a paper machine pressstructure, and more particularly, a divided press structure for a papermaking machine.

In the art of paper making it is conventional to form a wet fibrous Webon a suitable forming surface, such as a forming wire or a cylindermold, and the wet web is then passed from the forming surface throughone or more presses by conveying felts for carrying out preliminarydewatering of the web before it is transferred to the heated dryer drumor drums which are ordinarily used to obtain substantially the degree ofdryness desired in the final paper product. A number of structures havebeen proposed for the presses or the so-called press section, and theseinclude suction presses wherein the web is passed through a press nipdefined by at least one perforate suction roll which is ordinarilywrapped by a felt. Such presses often mark the web passing through thenip. In a divided press, the press nip receiving the web on a felt isnot defined by one or more suction rolls (so as to avoid any marking ofthe web) and the felt is separated from the web (after it carries" theWeb through the press nip) and passed through a felt only press whichreceives the felt without any web thereon and dewaters the same.

The instant invention relates to an improvement in the press sectionarrangement, and more particularly to an improvement in divided pressstructures. In the instant invention a divided press is provided whichis composed of only three rolls, as contrasted to a divided press havingone press couple defining a press for receiving the felt with the webthereon and a second press couple defining the felt only press (whichtwo press couples involve -a total of four rolls). In the instantinvention, the divided press unit comprises a first or middle press rollwhich defines with a second press roll a nip for receiving the felt withthe web thereon. This first press roll also defines a felt only pressnip with a third press roll which is a perforate suction press roll. Theperforate suction press roll defines the felt only nip with a surfaceportion of the first press roll that is substantially undeflected orsubjected to a minimum central deflection in the direction of such feltonly nip. As will be appreciated, the rather substantiallength-to-diameter ratio of press rolls in modern-day paper machinesresults in a tendency for such rolls to have a central downwarddeflection (of the centroidal axis thereof) by virtue of the weight ofthe roll itself, which may be referred to as its inherent deflection,and this tendency toward downward deflection is increased if a secondpress roll is positioned above the first roll and in press nip definingrelation therewith. vIn such instance there is a tendency for deflectionto occur in a generally downward direction, but not horizontally towardeither side of the roll. The instant invention contemplates thepositioning of the comparatively more delicate perforate suction rollshell so as to define a felt only press nip along one side of the firstroll, so that the suction press roll will not be subjected to the forcesresulting in a tendency toward additional downward central deflectionbecause of the first roll.

It is therefore an important object of the instant invention to providean improved divided press, and an improved press section containing oneor more divided presses.

Tis a further object to provide a divided press comprising a first roll,a second roll defining a first press nip with the first roll, a thirdroll defining a second press nip with one side of the first roll, and alooped traveling felt wrapping the first roll and carrying a web throughthe first nip, separating from the web at the off-running side of thefirst nip, and then passing through the second nip without the web todewater the felt thereat.

Still another object of the instant invention is to provide an improvedpress section comprising a first three press rolls defining therebetweena felt and web press nip and a felt only press nip, a second three pressrolls defining therebetween a felt and web press nip and a felt onlypressnip, a pickup felt conveying a wet web received from a formingsurface through the first felt and web press nip and then separatingfrom the web and passing through the first felt only press nip to bedewatered, and a press felt conveying the web separated from the pickupfelt through the second felt and web press nip and then separating fromthe web and passing through the second felt only press nip to bedewatered; each of the felt only presses being defined by a press rollwithin the loop of one of said felts and a perforate suction press rolloutside the loop of each of said felts and positioned at leastsubstantially as high as the press roll with which it defines the feltonly press nip.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed dislcosure thereof and the drawings attached heretoand made a part hereof.

As shown in the drawing, a fibrous wet web W is formed in conventionalmanner on a wire 10 passing over a couch roll 11 having a suction area1111 shown diagrammatically therein. The wire 10 passes over the suctionarea 11a of the couch roll 11 and then down around a turning roll 12.This provides a downwardly inclined reach 10a of wire from the couchroll 11 to the turning roll 12.

In its more specific aspects, the instant invention relates to a presssection indicated generally by the reference numeral 20, which comprisesa looped pickup felt 21, a

first suction pickup roll 22, with a suction area indicateddiagrammatically at 22a, within the loop of the pickup felt 21 andurging the felt 21 against the wet web W on the downwardly inclinedreach 16a of the forming surface or wire 10 to transfer the web W fromthe reach forming surface 10a to the underside of the reach of pickupfelt indicated at 21a. The first divided press indicated generally bythe reference numeral 30 is composed of a middle roll 31 that is a pressroll within the loop of the pickup felt 21, and a second roll 32directly beneath the middle roll 31 and outside of the pickup felt loop,which defines with the middle roll 31 a generally horizontal first pressnip N1 receiving the reach of pickup felt 21a with the web thereon (onthe underside). The first divided press also includes a third roll 33which is a perforate suction roll mounted directly above the middle roll31 and defining therewith a generally horizontal first felt only pressnip N-Z which receives the pickup felt 21 without the web and dewatersthe felt passing through the felt only nip N-Z. The pressure at the feltonly nip N-2 is maintained at least as high as the pressure at the feltand web nip N-l so as to satisfactorily effect the required dewatering0f the felt 21 passing through the felt only nip N-Z.

As is apparent from the drawing, the initial felt reach 21a carrying theweb W enters the nip N-1 from the oncoming side thereof and the feltreach 2111 at the off-running side of the nip N-l is separated from theweb W and guided by means of a plurality of guide rolls 22, 23, 24, 25and 26. The last guide roll 26 guides the reach of felt 21c approachingthe felt only nip N-2 at the oncoming side of the nip whereat the feltreach 21c Wraps a suction area shown diagrammatically at 33a in theperforate suction roll 33. The next reach of felt 21d extends from theoff-running side of the felt only nip N-2 on toward the suction pickuproll 22. At the off-running side of the felt only nip N-Z there isprovided a save-all 34 which is of areaerv 3 conventional structure andindicated diagrammatically to show that it will receive droplets ofwater retained in the perforations in the perforate shell at the suctionarea 33a and then thrown out of these perforations by centrifugal forceat the off-running region 33b of the perforate shell relative to the nipN-2.

As indicated in the drawing, the centers of each of the rolls 31, 32 and33 lie in substantially the same vertical plane P-1 and the nips N-1 andN-2 are substantially normal to the plane P-1 or substantiallyhorizontal. It will be appreciated, however, that although this is apreferred arrangement for the rolls 31, 32 and 33, particularly suitableresults may be obtained if the center lines of the rolls 31 and 32 andthe center lines of the rolls 31 and 33 in each case lie in the same ordifferent planes which are generally upwardly extending at least at anangle of about 45 from the horizontal, so that the rolls 31, 32 and 33may be described as generally superimposed, if not vertically aligned.The perforate suction roll 33 is not subjected to any exterior forcesapplying a downward loading force across the length thereof, which wouldtend to cause downward loading force across the length thereof, whichwould tend to cause downward deflection of the perforate shell. Theperforate shell for the roll 33 will, of course, tend to deflectdownwardly to a slight extent because of its own weight, but this can bereadily counteracted or compensated for by either permitting acorresponding deflection along the top of the intermediate roll 31 inthe region of the felt only nip N-2, or by the use of knownanti-deflection means in the mounting of the roll 31 to substantiallyeliminate any (downward) deflection across the width of the felt onlynip N-Z.

The instant press section also comprises a second divided pressindicated generally by the reference numeral which contains a loopedpress felt 51 having a conventional bottom run with associated guiderolls (not shown). The press 40 is also a three roll press comprising acentral press roll 41 within the loop of the press felt 51, and an upperpress roll 42 directly above the roll 41 and defining therewith a pressnip N3. The press 4t also comprises a suction press roll 43 generallyhorizontally aligned with the central press roll 41 so as to define anupwardly extending felt only press nip N4.

As shown, the felt 51 is guided by guide rolls 52, 53, 54 and 55. Theguide roll 53 aligns the reach 51a of the felt 51 at the oncoming sideof the nip N-3 and the reach 51a receives the web W at the off-runningside of the previously mentioned press nip N-1 as the web separates fromthe oif-running reach 21b of the pickup felt 21 and the off-running sideof the bare press roll 32. The web W is conveyed on the top of theoncoming reach felt 51a into the web and felt press nip N-3. At theoff-running side of the press nip N-3 the web W is carried away from theoff-running felt reach 51b, in this case by virtue of a tendency of theweb W to temporarily adhere to the bare surface of the upper press roll42; and the web then passes on to a conventional dryer arrangement, suchas is indicated in part by the first two dryer rolls 61 and 62. Theoff-running felt reach 51b is guided away from the central roll 41 bythe guide roll 54 and is then fed back into the felt only nip N4. At theoncoming side of the felt only nip N-4 the perforate suction roll 43 hasa conventional suction gland indicated diagrammatically at 43a, andwater droplets drawn into the perforations in the shell of the roll 43at the suction area 43:: are thrown back out of the shell into aconventional save-all indicated diagrammatically at 44 along thedown-running side of the perforate suction roll 43. As shown in thesecond divided press 40, an alternative felt run 51b around alternativefelt rolls 54'a and 54b is useful not only for separating the felt 51'bfrom the Web W at the off-running side of the nip N3 but also for use asa conveyor of broke when the web breaks at this location. The middlepress roll 41 with which the suction roll 43 defines the felt only pressnip N-4 is positioned beneath the bare press roll 42, so that as graniterolls or plain rubber covered rolls.

the application of press forces along the nip N-3 will have a tendencyto cause a downward deflection in the central or lower press roll 41. Ashas already been indicated, various known anti-deflection means may beemployed for mounting the roll 41, and these might include a centrallypositioned backup roll urging against the central part of the roll 41generally beneath the center line thereof in the region indicated at A,or such anti-deflection mounting means might include known force coupleapplying means connected to the bearings mounting the stub shafts of theroll for applying a bending force to the roll. Whether or not such meansare employed, the tendency toward deflection is generally verticallydownward in the central roll 41, and there is not a tendency to deflectthe central portion of the roll 41 toward the felt only nip N-4 oragainst the central portion of the rotary perforate shell of the suctionroll 43. In contrast, the suction roll 43 may define a uniform felt onlynip N-4 with the central roll 41, such nip N-4 having a substantiallyuniform pressure across the width thereof and, therefore, having asubstantially uniform dewatering effect. Again, the pressure at the nipN-4 is at least as great as the pressure at the nip N3, so thatdewatering may take effect.

The press rolls 41 and 42 may be suitably mounted on pressure loadingarms, which are indicated essentially diagrammatically in dotted linesat '70 and for the rolls 41 and 42, respectively. The journals 41a ofthe roll 40 may be carried on arms 70 pivotally mounted at 71 andactuated, for example, by air diaphragms 72 for loading the roll 41against the suction roll 43 to obtain the desired pressure at the feltonly nip N-4. Also, the journals 42a of the upper, bare press roll 42may be carried in arms 80 mounted on fixed pivots 81 and actuated by airdiaphragms 32 and $3 for selectively increasing or decreasing thepressure at the nip N-3. Similar conventional nip pressure controlmounting means are employed for the press rolls 31 and 32, so that thefelt only nip N-2 will be operated at at least as great a nip pressureas the pressure at the nip N-l. The absence of external loads (otherthan that of the roll 41) applied to the comparatively more delicate andflexible suction roll 43 thus simplifies the operation at the nip N4.

it will be appreciated that the instant invention provides a uniquethree-roll divided press arrangement for obtaining maximum efliciencyand maximum life for the perforate suction roll shells that are employedto engage and dewater the operating surface of the felts at the feltonly press. The perforate suction roll shells engage the same side ofthe felt 21 or 51 with their suction areas 33a and 43a, respectively,and this is the side of the felt 21 and 51 which is ultimately exposedto the fibrous web at the Web press nips N-1 and N-3, respectively, sothat it is this side of the felts 21 and 5-1 which will ordinarilyreceive fines (e.g. clay, etc.) and fibers which may separate from theweb during the treatment thereof. By applying the suction area to thisside of the felt 21 or 51, it will be appreciated that such foreignmatter accumulating on the felt surface will be most readily removed atthe felt only nips N-2 and N4 during the dewatering of the felt thereat.Showers S within the felt loops also assist in this function. The felt21 and 51 is in each case dewatered to the extent found to be mostsuitable for transfer of water from the web to the felt at the web pressnips -N-1 and N3.

The plain press rolls 32 and 42 to which the web W is actually exposedare preferably bare press rolls such The middle press rolls 31 and 41within the loop of the felts 21 and 51, respectively, may be plainrubber covered rolls, or rubber covered rolls with relatively fineporous all It will also be appreciated that in arrangements wherein therolls 3'1 and 32 or 41 and 42 defining the web nips N-1 or N3 aregenerally superimposed, the third perforate suction rolls 3 3 or 43 arepreferably positioned with their centers at least about as high as thecenter of the rolls 41 or 31 with which they define the felt only nipsN-2 and N-4, respectively. This results in a minimum effect of adeflection load against the perforate shells for the suction rolls 33and 43.

Also referring specifically to the second press 40, it will be notedthat the web W is guided from the off-running side of the press roll 32and onto the oncoming felt reach 51a by the positioning the guide roll53 at the oncoming side of the nip N-3. At the off-running side of thenip N-3, the dryer 61 also functions as a guide means for the web W andassists (depending to some etxent upon the inherent adherence betweenthe web W and the top bare press roll 42) in directing the web W awayfrom the off-running felt reach 51b. The guide roll 54, likewise,directs the off-running felt reach 51b away from the web (even insituations where the web W has substantially no adherence to the surfaceof the bare roll press 42).

It will also be appreciated that the first press 30 provides a transferpress nip N-1 which is also a press nip for receiving the pickup felt 21 and the web W and transferring the web from the pickup felt to thepress felt 51 (through an open draw and by means of the positioning ofthe guide roll 53) at the oncoming felt reach 51a.

In addition, the centers of the two rolls 4-1 and 42 defining the feltpress nip N-3 lie in a given upwardly extending plane P-Z (preferablyvertical), so that deflection forces will act primarily in this planeP-2. In the vertical alignment of the plane P-2 the deflection forcescaused by the weight of each of the rolls per se will also act in theplane P2, but if the plane P2 is not truly vertical there may bevertically aligned downward forces representing the weights of each ofthe rolls, coupled with a deflection force generated at the nip N-3 (bythe means 70 and 80) which will be aligned substantially in the planeP-2 of the center lines of the rolls. Accordingly, with the principaldeflecting forces in alignment with the plane P 2 of the center lines ofthe rolls 41 and 42, it is particularly desirable to align the centerlines of the rolls 41 and 43 in a plane P-3 that is substantially normalto the plane P-Z. In this way the principal deflecting force does notact in or against the roll 41 in the direction of the felt only nip N-4.As a matter of practice, the plane P-3 is aligned preferably atapproximately 90 to the plane P-2, but advantages of the instantinvention may be obtained by aligning the plane P-3 at an angle of 90plus or minus 30 to the plane P-2, i.e., at substantially 60 to 120 withthe plane P-r2.

It will also be appreciated that, if the roll 41 is provided with aporous surface such as a rubber covered surface with a myriad of minuteblind holes as shown in U.S.- Patent No. 3,023,805, or a relativelyincompressible wire or fabric covering, then there may be some tendencyfor water to remain temporarily in the porous surface of the roll at theimmediate off-running side of both the web nip N-3and the felt only nipN-4. In such instance save-alls 41b and 41c of conventional structureand provided with a close running trailing edge to function generally asa doctor may be used with advantage at the off-running sides of the nipsN-3 and N-4, respectively, and such save-alls 41b and 41c are showngenerally diagrammatically in the drawing.

The porous surface (if any) on the middle press rolls 31 and 41 ispreferably of such fine porosity that there is a minimum shadow markingeffect on the web W at the nips N-1 and N-3, respectively (and certainlysubstantially less than the pattern ordinarily imparted to a web by afelt covered perforate suction roll). Also, this porosity on the middlepress rolls 31 and 41 does not extend through the shell or surfacecovering into the interior of the roll, in that the pores therein are oflimited depth 6 (or expressed in other terms, the rolls have a coverclosing out fluid penetration to the central portion of the roll, suchthat the roll may be a plain-surfaced bare roll or one with the limitedfine porosity just described).

The cleaning, conditioning and dewatering that is accomplished at thefelt only nips N2 and N4 herein involves dewateri-ng to obtainpreferably 60 to 70% moisture content on a dry felt weight basis withthe best results being obtained at 65%. The use of the (divided) feltonly press nip N-Z with the first press nip N-l has distinct advantages.It has now been found that the suction pickup from the wire may beaccomplished using much drier felts than heretofore. The felt moisturecontent may thus be adjusted to optimum conditions (erg. 65% forconventional woven wool felts) for use at the web nip N-1 by adjustmentat the felt only nip N-Q. (prior to suction pickup); and the web nip N-1thus functions not only as a transfer press nip (which ordinarilyremoves little or no water) but also as a working press nip operatingunder adjusted predetermined conditions for best Water removal. This isa particular advantage of a divided press arrangement for the first webnip (i.e. N-il).

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

I claim as my invention:

1. In a paper machine, a first roll, a second roll defining a firstpress nip with the first roll, a third roll defining a second press nipwith one side of the first roll, a looped traveling felt wrapping thefirst roll and carrying .a web through the fir-st nip, separating fromthe web and the first roll surface at the off-running side of the firstnip, and then passing through the second nip without the web to dewatcrthe felt thereat; said third roll being a perforate suction roll havingan inherent downward deflection; said first and second rolls beingimperforate rolls; and means in control of loading pressures at thefirst and second nips with said means applying control-led loading tosaid first nip to impart to said first imperforate roll a deflection insubstantial alignment with the aforesaid inherent downward deflection ofsaid suction roll for application of substantially uniform pressures onthe felt across said second nip.

2. In a paper machine, a looped traveling press felt, a first rollwithin the loop of said felt, means depositing a wet web onto the feltand removing the web from the felt, a second press roll defining withthe first roll a substantially horizontal first press nip receiving saidfelt carrying the web thereon, a third perforate suction press rollhaving an inherent downward deflection and defining with one side of thefirst roll a felt only upwardly extending press nip receiving said feltwithout the Web to dewater the felt thereat, means for selectivelyloading the second press r-oll against the first press roll to align thedownward deflection thereof with that of said suction roll to provide auniform load across the aforesaid felt only nip, and felt guide meansseparating the felt from the first roll at the off-running side of thefirst nip and feeding the felt back into the second nip.

3. In a paper machine, a first roll, a second roll defining a firstpress nip with the first roll, a third roll defining a second press nipwith one side of the first roll, the center lines of the first andsecond rolls lying in an upwardly extending first plane and the centerlines of the first and third roll lying in a plane aligned atsubstantially 60 to with the first plane, and a looped traveling feltwrapping the firs-t roll and carrying a web through the first nip,separating from the web at the off-running side of the first nip, andthen passing through the second nip without the web to dewater the feltthereat, said third roll being a perforate suction roll having aninherent deflection, and means in control of the first nip loadimparting to said first roll a deflection substantially aligned withsaid inherent deflection of the aforesaid perforate 7 third roll forefiecting a substantially uniform crossmachine load at said secondpres-s nip, thereby aifording substantially uniform dewaterin g andconditioning across the width of the felt passing through said secondnip.

References Cited by the Examiner UNITED STATES PATENTS 8 FOREIGN PATENTS2,768 1897 Great Britain.

15,127 1903 Great Britain. 189,593 10/07 Germany. 680,349 2/40 Germany.

DONALL H. SYLVESTER, Primary Examiner.

MORRIS O. WOLK, Examiner.

1. IN A PAPER MACHINE, A FIRST ROLL, A SECOND ROLL DEFIN-